Flame tubes for gas turbine engines

ABSTRACT

A flame tube for a gas turbine engine includes a combustion chamber having generally oppositely directed air openings which generate upstream and downstream vortex zones in the chamber. Twin fuel sprayers supply fuel to the respective zones, whereby combustion conditions within each zone are separately maintained.

United States Patent [191 Grindley et a1.

[ FLAME FOR GAS TURBINE ENGINES [75] Inventors: William Grindley, Burnley; George Edward Bunn, Clitheroe; Alan Ormerod, Oswaldtwistle; Alwin Harrison, Burnley, all of England [73] Assignee: Joseph Lucas (Industries) Limited,

Birmingham, England [22] Filed: Nov. 5, 197 1 [21] Appl. No.: 196,160

[52] US. Cl 60/39.74 R, 60/3971, 60/3965 [51] Int. Cl. F02c 3/24 [58] Field of Search.. 60/3974 R, 39.65, 39.71

[56] References Cited UNITED STATES PATENTS 4/1960 Allen 60/3971 June 28, 1974 2,974,487 3/1961 Stokes 60/39.65 2,999,359 9/1961 Murray 60/3974 R 3,064,424 1 H1962 Tomlinson 60/39.65 3,430,443 3/1969 Richardson 60/3974 R 3,579,983 5/1971 Caruel 60/39.71 3,626,444 12/1971 Caruel 60/39.?1

Primary Examiner-Douglas Hart Attorney, Agent, or Firm-l-Iolman & Stern [5 7] ABSTRACT A flame tube for a gas turbine engine includes a com bustion chamber having generally oppositely directed air openings which generate upstream and downstream vortex zones in the chamber. Twin fuel sprayers supply fuel to the respective zones, whereby combustion conditions within each zone are separately maintained.

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ATTORNEYS FLAME TUBES FOR GAS TURBINE ENGINES This invention relates to flame tubes for gas turbine engines and has as an object to provide a flame tube having a satisfactory combustion efficiency over a wide range of fuel flow rates.

According to the invention a flame tube for a gas turbine engine comprises an annular casing, an inlet for the casing to which compressed air is, in use, supplied, an annular combustion chamber within the outer casing, a first set of openings in a wall of the combustion chamber adapted to direct an airflow into the combustion chamber generally radially thereof, a second set of openings in the chamber wall downstream of the said first set and oppositely directed thereto, an airflow through the said openings defining, in use, upstream and downstream toroidal vortex zones, and pairs of fuel supply means within the combustion chamber respectively operable to supply fuel to the upstream and downstream zones, the arrangement being such that the air/fuel ratio in each zone remains within acceptable limits, irrespective of the overall air/fuel ratio supplied to the engine.

Examples of flame tubes according to the invention will now be described with reference to the accompanying drawings in which:

FIG. 1 shows, somewhat diagrammatically, a part section through an annular flame tube;

FIGS. 2, 5, 8 and are sections through alternative fuel supply means;

FIGS. 3, 6, 9 and 11 are views on the correspondingly numbered arrows in FIGS. 2, 5, 8 and 10 respectively, and

FIGS. 4 and 7 are sections on the corresponding lines in FIGS. 2 and 5.

The flame tube shown in FIG. 1 has an annular outer casing 10 formed with an inlet 11 through which compressed air is, in use, supplied. Within the casing 10 is an annular combustion chamber 12 which is formed at its upstream end 13 so as to direct the greater part of the air into the annular spaces 14 between the chamber 12 and casing 10. The upstream end 13 has an opening 15 via which a proportion of the air can enter a cavity 16 of the chamber 12.

Adjacent the end 13 is a further cavity 17 in the chamber 12, the cavity 17 having an open end directed towards the inlet 11. Openings 18, 19 between the cavities l6, 17 respectively and the remainder of the chamber 12 have associated internal baffles 18a, 19a whereby air passing through the openings 18, 19 is directed along the inside wall of the chamber 12. Additional openings 20 in the walls of the chamber 12 also include means for directing airflow along the inside wall of the chamber.

Larger openings 21 into the chamber 12 are directed generally radially of the chamber 12. Airflow through openings 21 combines with flow through openings 18, 19, 20 to create a pair of toroidal vortex zones 22, 23 which respectively define first and second combustion zones within the chamber 12. Pairs of fuel sprayers, one of which is shown generally at 24, are adapted to direct atomised fuel jets 25, 26 into the first and second comi bustion zones respectively.

Supply of fuel to each of the pair of Sprayers 24 is separately controlled. In ground idling conditions the jet 26 to the second combustion zone is shut off, all combustion taking place in the first zone defined by the vortex 22. A very large air/fuel ratio may thereby exist for the engine as a whole whilethe ratio within the first combustion zone remains at a lower level consistent with a high combustion efficiency.

The amount of fuel delivered by the jet 26 is increased with increasing power demanded of the engine, the maximum flow of the jet 26 being about three times that of the jet 25. At maximum fuel flow from both jets 25, 26 the air/fuel ratio in each zone does not fall below a level at which combustion is substantially complete.

The flame tube described thus permits a wide range of air/fuel ratios to be used to meet varying engine operating conditions, while maintaining a high combustion efficiency over the whole of this range. It has in practice been found that air/fuel ratios between and 42.4, respectively corresponding to stand-off and take-off conditions, may be used while maintaining combustion efficiency at higher than 99 percent.

The alternative fuel supply means shown in FIGS. 2 to 4 is a vapouriser arrangement 30 mounted in the wall of an annular flame tube 31. Flame tube 31 is generally similar in form to the flame tube described with reference to FIG. 1 and operates as before to define a pair of toroidal vortex combustion zones 32, 33. There are, in fact, a plurality of vapouriser arrangements 30 at angularly spaced positions around the flame tube 31.

The vapouriser arrangement 30 comprises a passage 34 and a further, crescent-section passage 35 having a common wall with, the passage 34. Passage 34 has an outlet 37 extending through an opening 36 of the flame tube 31. Outlet 37 is directed radially of the flame tube 31 towards the combustion zone 33. Passage 35 communicates with a transversely extending passage 38 which terminates in a pair of outlets 39, 40 directed towards the combustion zone 32. Passages 34, 35 are formed so as to be substantially cylindrical externally and are surrounded by a sleeve 41 which provides a part annular air inlet 42. Outlets 37, 39, 40 and inlet 42 are positioned so that fluid flow therethrough will enhance the airflow within the flame tube creating the combustion zones 32, 33.

In use, an air-fuel mixture is supplied to the passages 34, 35. The fuel is vapourised by the heat of the flame tube and the air-vapour mixture is supplied to the combustion zones 32, 33.

The alternative form of vapouriser shown in FIGS. 5, 6 and 7 differs from that described above in that it is positioned centrally within a section of the annular flame tube. Passages 44, 45 have respective outlets 46, 47 positioned, as before, so that fluid flow therethrough reinforces the vortices in the respective combustion zones.

FIGS. 8 and 9 show yet another form of vapouriser. Each of a plurality of vapourisers 50 extends radially into the annular flame tube 51 and comprises a tubular member 52, a pair of transverse tubes 53, 54 communieating with member 52 and a pair of outlets 55, 56 associated with the tubes 53, 54 respectively and directed radially outwards of the flame tube 51. The member 52, tubes 53, 54 and outlets 55, 56 have a longitudinal division 57 to provide a pair of passages for fluid. The vapourisers 50 are positioned within the flame tube 51 at a position intermediate the combustion zoneswhich are defined within the flame tube as previously described and fluid flowing through the outlets 55,56 acts, as before, to reinforce the existing vortices. A fuel air mixture from the passages in the vapouriser 50 enters the adjacent combustion zone.

Another means for supplying fuel to the combustion chamber of the invention is shown in FIGS. and 11. An annular flame tube 60 is formed, as before, with air inlets which operate to define combustion zones 61, 62. The flame tube 60 is also formed with an internal annular gutter 63 into which extends a plurality of fuel supply pipes 64. The flame tube 60 is also formed with a plurality of air scoops 65 having radially directed downstream ends 66 and into which extend fuel pipes 67.

In use, fuel enters the gutter 63 and scoops 65 and spills from the downstream openings thereof into the respective vortices of the zones 61, 62. The fuel is at least partly vaporised by heat from the flame tube before spilling into the combustion zones.

We claim:

l. A flame tube for a gas turbine engine, comprising an annular outer casing, an inlet for the casing to which compressed air is, in use, supplied, an annular combustion chamber within the outer casing, said combustion chamber having an upstream end axially spaced from a downstream end thereof relative to the general direction of flow of gases through the flame tube in use, a first set of openings in a wall of the combustion chamber adapted to direct an air flow into the combustion chamber generally radially thereof, a second set of openings in the chamber wall downstream of the said first set and oppositely directed thereto, said first and second sets of openings being arranged so that, in use, an air flow therethrough finds a single upstream toroidal vortex zone and a single downstream toroidal vortex zone, and pairs of fuel supply means mounted in the wall of the combustion chamber and respectively operable to supply fuel to the upstream and downstream zones, the arrangement being such that the air/fuel ratio in each zone remains within acceptable limits, ir-

respective of the overall air/fuel ratio supplied to the engine, said flame tube including a third set of openings in the chamber wall and baffles within said wall adapted to direct air flow through said third openings along the inside of the wall, and further including means defining a cavity externally of said chamber and communicating therewith by means of said third openmgs.

2. The flame tube according to claim 3 which includes a plurality of said cavities.

3. A flame tube for a gas turbine engine, comprising an annular outer casing, an inlet for the casing to which compressed air is, in use, supplied, an annular combustion chamber within the outer casing, said combustion chamberhaving an upstream end axially spaced from a downstream end thereof relative to the general direction of flow of gases through the flame tube in use, a first set of openings in a wall of the combustion chamber adapted to direct an air flow into the combustion chamber generally radially thereof, a second set of openings in the chamber wall downstream of the said first set and oppositely directed thereto, said first and second sets of openings being arranged so that, in use, an air flow therethrough finds a single upstream toroidal vortex zone and a single downstream toroidal vortex zone, and pairs of fuel supply means mounted in the wall of the combustion chamber and respectively operable to supply fuel to the upstream and downstream zones, wherein said fuel supply means comprises vapoun'ser arrangements, said flame tube including a third set of openings in the chamber wall and baffles within said wall adapted to direct air flow through said third openings along the inside of the wall and in which each pair of fuel supply means comprises a pair of passages whose respective outlets are positioned so that flows therethrough enhance the air flows through the second and third sets of openings respectively.

4. The flame tube according to claim 3 in which one of said passages in each pair has a portion extending transversely of the combustion chamber axis, and a pair of outlets at respective ends of the transverse portion.

5. The flame tube according to claim 4 in which the other of said passages in each pair extends through an associated one of said second openings.

6. The flame tube according to claim 3 in which the said passages have a common wall over at least part of their lengths.

7. The flame tube according to claim 6 in which one of the passages lies substantially within the other of the passages.

8. The flame tube according to claim 7 which includes a sleeve surrounding the said other passage and defining an air inlet for the combustion chamber.

9. A flame tube for a gas turbine engine, comprising an annular outer casing, an inlet for the casing to which compressed air is, in use, supplied, an annular combustion chamber within the outer casing, said combustion chamber having an upstream end axially spaced from a downstream end thereof relative to the general direction of flow of gases through the flame tube in use, a first set of openings in a wall of the combustion chamber adapted to direct an air flow into the combustion chamber generally radially thereof, a second set of openings in the chamber wall downstream of the said first set and oppositely directed thereto, said first and second sets of openings being arranged so that, in use, an air flow therethrough finds a single upstream toroidal vortex zone and a single downstream toroidal vortex zone, and pairs of fuel supply means mounted in the wall of the combustion chamber and respectively operable to supply fuel to the upstream and downstream zones, said flame tube further including an annular gutter and a plurality of air scoops whose downstream ends are directed radially of the combustion chamber, and in which each pair of fuel supply means comprises a pair of passages having outlets respectively lying within said gutter and within an associated air scoop, whereby, in use, air flows through said gutter and said scoops enhancing the upstream and downstream vortices respectively. 

1. A flame tube for a gas turbine engine, comprising an annular outer casing, an inlet for the casing to which compressed air is, in use, supplied, an annular combustion chamber within the outer casing, said combustion chamber having an upstream end axially spaced from a downstream end thereof relative to the general direction of flow of gases through the flame tube in use, a first set of openings in a wall of the combustion chamber adapted to direct an air flow into the combustion chamber generally radially thereof, a second set of openings in the chamber wall downstream of the said first set and oppositely directed thereto, said first and second sets of openings being arranged so that, in use, an air flow therethrough finds a single upstream toroidal vortex zone and a single downstream toroidal vortex zone, and pairs of fuel supply means mounted in the wall of the combustion chamber and respectively operable to supply fuel to the upstream and downstream zones, the arrangement being such that the air/fuel ratio in each zone remains within acceptable limits, irrespective of the overall air/fuel ratio supplied to the engine, said flame tube including a third set of openings in the chamber wall and baffles within said wall adapted to direct air flow through said third openings along the inside of the wall, and further including means defining a cavity externally of said chamber and communicating therewith by means of said third openings.
 2. The flame tube according to claim 3 which includes a plurality of said cavities.
 3. A flame tube for a gas turbine engine, comprising an annular outer casing, an inlet for the casing to which compressed air is, in use, supplied, an annular combustion chamber within the outer casing, said combustion chamber having an upstream end axially spaced from a downstream end thereof relative to the general direction of flow of gases through the flame tube in use, a first set of openings in a wall of the combustion chamber adapted to direct an air flow into the combustion chamber generally radially thereof, a second set of openings in the chamber wall downstream of the said first set and oppositely directed thereto, said first and second sets of openings being arranged so that, in use, an air flow therethrough finds a single upstream toroidal vortex zone and a single downstream toroidal vortex zone, and pairs of fuel supply means mounted in the wall of the combustion chamber and respectively operable to supply fuel to the upstream and downstream zones, wherein said fuel supply means comprises vapouriser arrangements, said flame tube including a third set of openings in the chamber wall and baffles within said wall adapted to direct air flow through said third openings along the inside of the wall and in which each pair of fuel supply means comprises a pair of passages whose respective outlets are positioned so that flows therethrough enhance the air flows through the second and third sets of openings respectively.
 4. The flame tube according to claim 3 in which one of said passages in each pair has a portion extending transversely of the combustion chamber axis, and a pair of outlets at respective ends of the transverse portion.
 5. The flame tube according to claim 4 in which the other of said passages in each pair extends through an associated one of said second openings.
 6. The flame tube according to claim 3 in which the said passages have a common wall over at least part of their lengths.
 7. The flame tube according to claim 6 in which one of the passages lies substantially within the other of the passages.
 8. The flame tube according to claim 7 which includes a sleeve surrounding the said other passage and defining an air inlet for the combustion chamber.
 9. A flame tube for a gas turbine engine, comprising an annular outer casing, an inlet for the casing to which compressed air is, in use, supplied, an annular combustion chamber within the outer casing, said combustion chamber having an upstream end axially spaced from a downstream end thereof relative to the general direction of flow of gases through the flame tube in use, a first set of openings in a wall of the combustion chamber adapted to direct an air flow into the combustion chamber generally radially thereof, a second set of openings in the chamber wall downstream of the said first set and oppositely directed thereto, said first and second sets of openings being arranged so that, in use, an air flow therethrough finds a single upstream toroidal vortex zone and a single downstream toroidal vortex zone, and pairs of fuel supply means mounted in the wall of the combustion chamber and respectively operable to supply fuel to the upstream and downstream zones, said flame tube further including an annular gutter and a plurality of air scoops whose downstream ends are directed radially of the combustion chamber, and in which each pair of fuel supply means comprises a pair of passages having outlets respectively lying within said gutter and within an associated air scoop, whereby, in use, air flows through said gutter and said scoops enhancing the upstream and downstream vortices respectively. 